Twenty minutes into his State of the Union address last week, President Obama entered the realm of uber-geekery — three-dimensional printing. The magical devices capable of printing prosthetics, violins and even aircraft parts have the potential, the president said, “to revolutionize the way we make almost everything.”

Forty miles away from the Capitol, in Glen Burnie, Md., Travis Lerol is proving Obama’s point — with guns.

In a spare bedroom, where an AR-15 rifle leans against the wall, Lerol is using a 3-D printer no larger than an espresso machine to make plastic rifle parts and ammunition magazines in between tea sets and chess pieces. The parts print, layer over layer, creating objects like an ink-jet printer etches words.

The 30-year-old software engineer said he has no plans to print anything outlawed by the government. But like many other gun owners, he is nervous that the push for gun control in the wake of the Sandy Hook Elementary School massacre will infringe on his Second Amendment rights.

Three-dimensional printers offer a potentially easy way around restrictions and registrations — a source of growing consternation among gun-control advocates and some allies in Congress.

“There’s really no one controlling what you do in your own home,” Lerol said.